December 27, 2013
Illness-Causing Bacteria More Persistent On Inanimate Objects Than Previously Believed
redOrbit Staff & Wire Reports - Your Universe Online
Two types of Streptococcus bacteria responsible for many sore throats and other, more serious infections persist on surfaces far longer than previously believed, according to new research appearing in Thursday’s edition of the journal Infection and Immunity.
Previous studies have determined that the bacteria in question, Streptococcus pneumoniae and Streptococcus pyogenes, are unable to live for long outside of the human body. Thus, experts have long believed that the pathogens would be unable to linger on objects such as toys, books, dishes or furniture.
However, senior author Dr. Anders Hakansson, an assistant professor of microbiology and immunology at the University of Buffalo, and his colleagues show that both types of Streptococcus can survive on objects and surfaces far longer than previously believed. Their findings suggest that extra steps might be required to prevent infections at hospitals, schools and daycare centers.
“These findings should make us more cautious about bacteria in the environment since they change our ideas about how these particular bacteria are spread,” Dr. Hakansson said. “This is the first paper to directly investigate that these bacteria can survive well on various surfaces, including hands, and potentially spread between individuals.”
According to the study authors, S. pneumoniae is one of the primarily causes of ear infections in children, and is often responsible for respiratory tract infection-related morbidity and mortality in both youngsters and the elderly. It is said to be widespread throughout daycare centers and is a common cause of hospital infections.
Furthermore, S. pneumoniae is responsible for causing pneumonia and sepsis linked to the deaths of an estimated one million kids in developing nations. S. pyogenes, on the other hand, is a common cause of strep throat and skin-based infections in school kids, and can cause serious ailments in adults as well, they explained.
As part of their research, Dr. Hakansson and his colleagues examined a daycare center in search of the two types of bacteria. Of the five stuffed toys they looked at, four of them tested positive for S. pneumonaie. Furthermore, they found S. pyogenes on cribs and several other surfaces, several of which had already been cleaned. The testing was conducted prior to the opening of the facility in the morning, meaning there had been no recent human contact.
“Bacterial colonization doesn't, by itself, cause infection but it's a necessary first step if an infection is going to become established in a human host,” the senior author explained. “Children, the elderly and others with compromised immune systems are especially vulnerable to these infections.”
He noted that previous research examining the lifespan of bacteria on inanimate objects used cultures that had been grown in laboratory conditions. These cultures, known as broth-grown planktonic bacteria, without fail tend to show that the bacteria quickly die out. However, Dr. Hakansson said that his team knew that this might not be representative of how the pathogens actually grow inside of a host.
“Since discovering that biofilms are key to the pathogenesis of S. pneumoniae, we wanted to find out how well biofilm bacteria survive outside the body,” he said. His team discovered that month-old biofilm of S. pneumoniae and S. pyogenes from contaminated surfaces were able to colonize within mice. They also found that biofilms could last hours on human hands, and remained on books, surfaces and toys in daycare centers, even after a cleaning.
“In all of these cases, we found that these pathogens can survive for long periods outside a human host,” the doctor added. “Commonly handled objects that are contaminated with these biofilm bacteria could act as reservoirs of bacteria for hours, weeks or months, spreading potential infections to individuals who come in contact with them.”
Dr. Hakansson said that additional research is necessary to fully grasp the conditions under which such contact could cause the bacteria to spread from one person to another.
“If it turns out that this type of spread is substantial, then the same protocols that are now used for preventing the spread of other bacteria, such as intestinal bacteria and viruses, which do persist on surfaces, will need to be implemented especially for people working with children and in health-care settings,” he concluded.
Image 2 (below): This SEM image shows a mature pneumococcal biofilm: the nearly round structures of S. pneumoniae bacteria are organizing a matrix of smaller, oddly shaped materials surrounding them that makes them more resistant to environmental stresses and antimicrobial agents. Credit: Laura Marks